Modern vehicles are typically configured as either two- or all-wheel drive. Either type of vehicle may employ a conventional powertrain, where a single engine is used to propel the vehicle, or a hybrid powertrain, where two or more distinct power sources, such as an internal combustion engine and an electric motor, are used to accomplish the same task. Furthermore, a multi-speed automatically-shiftable transmission may be employed as part of either type of a powertrain, and may thus be used in a hybrid vehicle with all-wheel drive.
In order to maximize fuel efficiency of a hybrid powertrain, the vehicle's engine may be shut off when engine torque is not required for driving the vehicle. Such a situation may be encountered when the hybrid vehicle is maintaining a steady cruising speed, is in a coast down mode, i.e., when the vehicle is decelerating from elevated speeds, or is stopped.